Many products are often manufactured in a continuous web format for the processing efficiencies and capabilities that can be achieved with that approach. The term “web” is used here to describe thin materials which are manufactured or processed in continuous, flexible strip form. Illustrative examples include thin plastics, paper, textiles, metals, and composites of such materials.
Such operations typically entail use of one or more, frequently many more, rollers (sometimes referred to as rolls) around which the web is conveyed throughout the process through a series of treatments, manufacturing steps, etc. Rollers are used for many purposes, including, for example, turning the direction of the web, applying pressure to the web in nip stations, positioning the web for travel through coating and other treatment stations, positioning multiple webs for lamination, stretching webs, etc. Rollers used in such operations are made of a variety of materials, with the selection dependent in large part upon the web(s) being handled, the operational parameters (e.g., speed, temperature, humidity, tension, etc.). Some illustrative examples of materials used to make rollers or covering surfaces thereon include rubber, plastics, metal (e.g., aluminum, steel, tungsten, etc.), foam, felt, and woven fabrics. Specific rollers may be configured to be free rolling, powered (in the same direction the web is traveling or opposite direction, at the same or different speed than the web is traveling, etc.), etc. depending upon the desired tension parameters.
It has been known to texture the surface of rollers to improve web conveyance properties. For example, U.S. Pat. No. 4,426,757 (Hourticolon et al.) and U.S. Pat. Nos. 4,910,843, 4,914,796, and 4,970,768 (all Lioy et al.) disclose forming cavities in the surface of rollers to ameliorate the effects of air carried by fast moving web.
New generation products entail ever more rigorous and precise specifications. Ever more stringent quality control specifications require higher performing processes. Manufacturers using web handling seemingly continually seek higher web processing speeds. The need exists for improved web transport and web handling methods and apparatuses, particularly for use in the high speed, high capacity manufacture and handling of demanding web materials such as optical films and other specialty plastic materials.